This invention relates to displacement converters which are useful in pressure gauges or similar instruments, and more particularly to a displacement converter which includes a displacement detector of simplified construction, making it possible to produce a low cost pressure gauge. A displacement converter in accordance with the invention corrects for nonlinearities in the displacement detection signal resulting from its simplified structure to yield a linearized electrical signal.
Capacitive-type displacement detectors have heretofore been used in pressure gauges. In a conventional capacitive-type displacement detector, diaphragms are provided as pressure-sensing elements at both ends of a cylindrical container, a coupling shaft being bridged between these diaphragms. A movable electrode is supported on the coupling shaft at the center thereof, with fixed electrodes insulated from the container mounted on opposing sides of the movable electrode. An electrical signal is generated which corresponds to the difference in the capacitance values between the movable electrode and each of the fixed electrodes, thereby indicating the difference between the respective pressures applied to the sensing diaphragms.
In other words, the conventional capacitive-type displacement detector is constructed and functions as a differential pressure gauge. Even if one wishes merely to measure the pressure of a gas or a liquid, use must be made of a displacement detector having a differential pressure construction. A capacitive-type displacement detector of differential pressure construction is structurally complicated and costly, and therefore represents an uneconomical approach for merely measuring pressure.
While it is possible to simplify the structure of a capacitive-type displacement detector and thereby reduce its cost, a simplified detector structure, as will later be explained, exhibits a non-linear relationship between the applied pressure and the resultant electrical signal so that the output thereof is not an accurate representation of pressure.